.beta.-Lactam antibiotics represented by thienamycin have derives weight as medicines from their broad antimicrobial spectra, and various types of .beta.-lactam antibiotics have been studied.
Among the developed .beta.-lactam antibiotics, those having a vinylidene group or an acetylene group at the 3-position of the azetidin-2-one skeleton have recently attracted attention (refer to Tetrahedron Lett., Vol. 29, p. 5053 (1988), J. Chem. Soc., Chem. Commun., p. 294 (1990), and ibid., p. 1066 (1984)). There has been a demand, accordingly, for an industrially advantageous process for preparing an azetidin-2-one derivative having a vinylidene group or an acetylene group at the 3-position which is an intermediate for synthesizing .beta.-lactam antibiotics of this type.
Known processes for preparing azetidin-2-one derivatives having a vinylidene group at the 3-position include a process shown in reaction scheme A below, which comprises alkylating the nitrogen atom of a 3-alkylidene-azetidin-2-one compound, chlorinating the product with t-butyl hypochlorite, and subjecting the resulting compound to desilylation and dechlorination simultaneously to prepare a 3-vinylidene-azetidin-2-one derivative in a percent yield of from 36 to 68% (refer to J. Chem. Soc.. Chem. Commun., p. 735 (1987)). ##STR8## wherein Me represents a methyl group; and R.sup.9 represents a methyl group, a benzyl group, or a substituted benzyl group.
Known processes for preparing azetidin-2-one derivatives having an acetylene group at the 3-position include a process shown in reaction scheme B below, which comprises reacting a di(phenylacetyl)cyclohexadiene derivative with zinc chloride in a carbon tetrachloride solvent to obtain a bicyclo[2.2.2]octadienone derivative in a percent yield of 60%, thermally decomposing the product to obtain an alkenylketene, and reacting the alkenylketene with N-phenylbenzylideneimine to obtain the desired compound in a yield of 72% (refer to Tetrahedron Lett., Vol. 29, p. 2765 (1988)); and a process shown in reaction scheme C below, which comprises reacting a 2,5-dialkynyl-3,6-dichloro-1,4-benzoquinone with an azide ion to obtain a diazidoquinone and reacting the resulting compound in a carbon tetrachloride solvent in the presence of dicyclohexylcarbodiimide (DCC) to obtain a desired compound with the percent yield of the latter reaction being from 42 to 86% (refer to J. Org. Chem., Vol. 52, p. 1315 (1987) and J. Chem. Soc., Chem. Commun., p. 1066 (1984)). ##STR9## wherein R.sup.10 represents a hydrogen atom or a trimethylsilyl group; and Ph represents a phenyl group. ##STR10## wherein R.sup.11 represents an n-butyl group, a phenyl group, a substituted phenyl group, a phenethyl group, etc.
However, any of these known processes involves long reaction steps and is therefore not suitable for industrial production.
It is known, on the other hand, that .beta.-lactam compounds are synthesized through various techniques, such as cyclization of a .beta.-amino acid, cyclization of a halogenated propanamide, reaction between an enol silyl ether and chlorosulfonyl isocyanate, and reaction between an imine and a diketene (refer to Chem. Soc. Rev., Vol. 5, p. 181 (1976), YUKI GOSEI KAGAKU, Vol. 47, p. 606 (1989), etc.). Among these known processes is included a process shown in reaction scheme D, in which a 2-bromo-3-aminopropene derivative is reacted with carbon monoxide to conduct carbonylation and lactamization at the same time (refer to J. Chem. Soc., Chem. Commun., p. 698 (1979)). ##STR11## wherein R.sup.12 a hydrogen atom or a phenyl group; R.sup.13 represents a benzyl group, a phenethyl group, etc.; and Ph represents a phenyl group.